Protein identification and proteomics are important new tools in cancer research. The Protein Mass Spectrometry Shared Resource will provide high-level mass spectrometry of biomolecules and protein analyses. This Shared Resource is based around a pair of tandem mass analyzers (the AB 4700 MALDITOF/ TOF and Thermo LTQ nanoESI-QIT), with access to as many as ten HPLC systems containing 10 quaternary and two binary pumps, seven PCs running at least 21 software packages, and numerous smaller items. The Facility is able to routinely identify proteins in slices from polyacryamide gels. In addition, it can routinely identify proteins in pull-down mixtures, complex virions, and whole cell extracts. They have done multi-dimensional (up to three dimensions) of tandem HPLC prior to LC-MALDI analysis. This capability includes two-dimensional protein fractionation (PF2D) and two and three dimensions of tandem peptide fractionation. This Facility provides an exciting springboard to the frontiers of state-of-the art proteomics. The Protein Mass Spectrometry Facility has been supported by the Cancer Center as a developing Shared Fesource for the past three years. Permanent funds are now requested for support as a full Shared Resource.